1 files changed, 1 insertions, 1 deletions
diff --git a/lib/Support/Windows/Windows.h b/lib/Support/Windows/Windows.h
index 5c1da0d617..2ddd15efa1 100644
--- a/lib/Support/Windows/Windows.h
+++ b/lib/Support/Windows/Windows.h
@@ -75,7 +75,7 @@ public:
   }
 
   // True if Handle is valid.
-  operator bool() const {
+  LLVM_EXPLICIT operator bool() const {
     return HandleTraits::IsValid(Handle) ? true : false;
   }